The present invention relates generally to pharmaceutical products and methods and, more specifically, to methods and compositions suitable for increasing the mineral content of bone. Such compositions and methods may be utilized to treat a wide variety of conditions, including for example, osteopenia, osteoporosis, fractures and other disorders in which low bone mineral density are a hallmark of the disease.
Two or three distinct phases of changes to bone mass occur over the life of an individual (see Riggs, West J. Med. 154:63-77, 1991). The first phase occurs in both men and women, and proceeds to attainment of a peak bone mass. This first phase is achieved through linear growth of the endochondral growth plates, and radial growth due to a rate of periosteal apposition. The second phase begins around age 30 for trabecular bone (flat bones such as the vertebrae and pelvis) and about age 40 for cortical bone (e.g., long bones found in the limbs) and continues to old age. This phase is characterized by slow bone loss, and occurs in both men and women. In women, a third phase of bone loss also occurs, most likely due to postmenopausal estrogen deficiencies. During this phase alone, women may lose an additional 10% of bone mass from the cortical bone and 25% from the trabecular compartment (see Riggs, supra).
Loss of bone mineral content can be caused by a wide variety of conditions, and may result in significant medical problems. For example, osteoporosis is a debilitating disease in humans characterized by marked decreases in skeletal bone mass and mineral density, structural deterioration of bone including degradation of bone microarchitecture and corresponding increases in bone fragility and susceptibility to fracture in afflicted individuals. Osteoporosis in humans is preceded by clinical osteopenia (bone mineral density that is greater than one standard deviation but less than 2.5 standard deviations below the mean value for young adult bone), a condition found in approximately 25 million people in the United States. Another 7-8 million patients in the United States have been diagnosed with clinical osteoporosis (defined as bone mineral content greater than 2.5 standard deviations below that of mature young adult bone). Osteoporosis is one of the most expensive diseases for the health care system, costing tens of billions of dollars annually in the United States. In addition to health care-related costs, long-term residential care and lost working days add to the financial and social costs of this disease. Worldwide approximately 75 million people are at risk for osteoporosis.
The frequency of osteoporosis in the human population increases with age, and among Caucasians is predominant in women (who comprise 80% of the osteoporosis patient pool in the United States). The increased fragility and susceptibility to fracture of skeletal bone in the aged is aggravated by the greater risk of accidental falls in this population. More than 1.5 million osteoporosis-related bone fractures are reported in the United States each year. Fractured hips, wrists, and vertebrae are among the most common injuries associated with osteoporosis. Hip fractures in particular are extremely uncomfortable and expensive for the patient, and for women correlate with high rates of mortality and morbidity.
Although osteoporosis has been defined as an increase in the risk of fracture due to decreased bone mass, none of the presently available treatments for skeletal disorders can substantially increase the bone density of adults. There is a strong perception among all physicians that drugs are needed which could increase bone density in adults, particularly in the bones of the wrist, spinal column and hip that are at risk in osteopenia and osteoporosis.
Current strategies for the prevention of osteoporosis may offer some benefit to individuals but cannot ensure resolution of the disease. These strategies include moderating physical activity (particularly in weight-bearing activities) with the onset of advanced age, including adequate calcium in the diet, and avoiding consumption of products containing alcohol or tobacco. For patients presenting with clinical osteopenia or osteoporosis, all current therapeutic drugs and strategies are directed to reducing further loss of bone mass by inhibiting the process of bone absorption, a natural component of the bone remodeling process that occurs constitutively.
For example, estrogen is now being prescribed to retard bone loss. There is, however, some controversy over whether there is any long term benefit to patients and whether there is any effect at all on patients over 75 years old. Moreover, use of estrogen is believed to increase the risk of breast and endometrial cancer.
High doses of dietary calcium, with or without vitamin D has also been suggested for postmenopausal women. However, high doses of calcium can often have unpleasant gastrointestinal side effects, and serum and urinary calcium levels must be continuously monitored (see Khosla and Rigss, Mayo Clin. Proc. 70:978-982, 1995).
Other therapeutics which have been suggested include calcitonin, bisphosphonates, anabolic steroids and sodium fluoride. Such therapeutics however, have undesirable side effects (e.g., calcitonin and steroids may cause nausea and provoke an immune reaction, bisphosphonates and sodium fluoride may inhibit repair of fractures, even though bone density increases modestly) that may prevent their usage (see Khosla and Rigss, supra).
No currently practiced therapeutic strategy involves a drug that stimulates or enhances the growth of new bone mass. The present invention provides compositions and methods which can be utilized to increase bone mineralization, and thus may be utilized to treat a wide variety of conditions where it is desired to increase bone mass. Further, the present invention provides other, related advantages.
As noted above, the present invention provides a novel class or family of TGF-beta binding-proteins, as well as assays for selecting compounds which increase bone mineral content and bone mineral density, compounds which increase bone mineral content and bone mineral density and methods for utilizing such compounds in the treatment or prevention of a wide variety of conditions.
Within one aspect of the present invention, isolated nucleic acid molecules are provided, wherein said nucleic acid molecules are selected from the group consisting of: (a) an isolated nucleic acid molecule comprising sequence ID Nos. 1, 5, 7, 9, 11, 13, or, 15, or complementary sequence thereof; (b) an isolated nucleic acid molecule that specifically hybridizes to the nucleic acid molecule of (a) under conditions of high stringency; and (c) an isolated nucleic acid that encodes a TGF-beta binding-protein according to (a) or (b). Within related aspects of the present invention, isolated nucleic acid molecules are provided based upon hybridization to only a portion of one of the above-identified sequences (e.g., for (a) hybridization may be to a probe of at least 20, 25, 50, or 100 nucleotides selected from nucleotides 156 to 539 or 555 to 687 of Sequence ID No. 1). As should be readily evident, the necessary stringency to be utilized for hybridization may vary based upon the size of the probe. For example, for a 25-mer probe high stringency conditions could include: 60 mM Tris pH 8.0, 2 mM EDTA, 5xc3x97Denhardt""s, 6xc3x97SSC, 0.1% (w/v) N-laurylsarcosine, 0.5% (w/v) NP-40 (nonidet P-40) overnight at 45 degrees C., followed by two washes with with 0.2xc3x97SSC/0.1% SDS at 45-50 degrees. For a 100-mer probe under low stringency conditions, suitable conditions might include the following: 5xc3x97SSPE, 5xc3x97Denhardt""s, and 0.5% SDS overnight at 42-50 degrees, followed by two washes with 2xc3x97SSPE (or 2xc3x97SSC)/0.1% SDS at 42-50 degrees.
Within related aspects of the present invention, isolated nucleic acid molecules are provided which have homology to Sequence ID Nos. 1, 5, 7, 9, 11, 13, or 15, at a 50%, 60%, 75%, 80%, 90%, 95%, or 98% level of homology utilizing a Wilbur-Lipman algorithm. Representative examples of such isolated molecules include, for example, nucleic acid molecules which encode a protein comprising Sequence ID NOs. 2, 6, 10, 12, 14, or 16, or have homology to these sequences at a level of 50%, 60%, 75%, 80%, 90%, 95%, or 98% level of homology utilizing a Lipman-Pearson algorithm.
Isolated nucleic acid molecules are typically less than 100 kb in size, and, within certain embodiments, less than 50 kb, 25 kb, 10 kb, or even 5 kb in size. Further, isolated nucleic acid molecules, within other embodiments, do not exist in a xe2x80x9clibraryxe2x80x9d of other unrelated nucleic acid molecules (e.g., a subclone BAC such as described in GenBank Accession No. AC003098 and EMB No. AQ171546). However, isolated nucleic acid molecules can be found in libraries of related molecules (e.g., for shuffling, such as is described in U.S. Pat. Nos. 5,837,458; 5,830,721; and 5,811,238). Finally, isolated nucleic acid molecules as described herein do not include nucleic acid molecules which encode Dan, Cerberus, Gremlin, or SCGF (U.S. Pat. No. 5,780,263).
Also provided by the present invention are cloning vectors which contain the above-noted nucleic acid molecules, and expression vectors which comprise a promoter (e.g., a regulatory sequence) operably linked to one of the above-noted nucleic acid molecules. Representative examples of suitable promoters include tissue-specific promoters, and viralxe2x80x94based promoters (e.g., CMV-based promoters such as CMV I-E, SV40 early promoter, and MuLV LTR). Expression vectors may also be based upon, or derived from viruses (e.g., a xe2x80x9cviral vectorxe2x80x9d). Representative examples of viral vectors include herpes simplex viral vectors, adenoviral vectors, adenovirus-associated viral vectors and retroviral vectors. Also provided are host cells containing or comprising any of above-noted vectors (including for example, host cells of human, monkey, dog, rat, or mouse origin).
Within other aspects of the present invention, methods of producing TGF-beta binding-proteins are provided, comprising the step of culturing the aforementioned host cell containing vector under conditions and for a time sufficient to produce the TGF-beta binding protein. Within further embodiments, the protein produced by this method may be further purified (e.g., by column chromatography, affinity purification, and the like). Hence, isolated proteins which are encoded by the above-noted nucleic acid molecules (e.g., Sequence ID NOs. 2, 4, 6, 8, 10, 12, 14, or 16) may be readily produced given the disclosure of the subject application.
It should also be noted that the aforementioned proteins, or fragments thereof, may be produced as fusion proteins. For example, within one aspect fusion proteins are provided comprising a first polypeptide segment comprising a TGF-beta binding-protein encoded by a nucleic acid molecule as described above, or a portion thereof of at least 10, 20, 30, 50, or 100 amino acids in length, and a second polypeptide segment comprising a non-TGF-beta binding-protein. Within certain embodiments, the second polypeptide may be a tag suitable for purification or recognition (e.g., a polypeptide comprising multiple anionic amino acid residuesxe2x80x94see U.S. Pat. No. 4,851,341), a marker (e.g., green fluorescent protein, or alkaline phosphatase), or a toxic molecule (e.g., ricin).
Within another aspect of the present invention, antibodies are provided which are capable of specifically binding the above-described class of TGF-beta binding proteins (e.g., human BEER). Within various embodiments, the antibody may be a polyclonal antibody, or a monoclonal antibody (e.g., of human or murine origin). Within further embodiments, the antibody is a fragment of an antibody which retains the binding characteristics of a whole antibody (e.g., an F(abxe2x80x2)2, F(ab)2, Fabxe2x80x2, Fab, or Fv fragment, or even a CDR). Also provided are hybridomas and other cells which are capable of producing or expressing the aforementioned antibodies.
Within related aspects of the invention, methods are provided detecting a TGF-beta binding protein, comprising the steps of incubating an antibody as described above under conditions and for a time sufficient to permit said antibody to bind to a TGF-beta binding protein, and detecting the binding. Within various embodiments the antibody may be bound to a solid support to facilitate washing or separation, and/or labeled. (e.g., with a marker selected from the group consisting of enzymes, fluorescent proteins, and radioisotopes).
Within other aspects of the present invention, isolated oligonucleotides are provided which hybridize to a nucleic acid molecule according to Sequence ID NOs. 1, 3, 5, 7, 9, 11, 13, 15, 17, or 18 or the complement thereto, under conditions of high stringency. Within further embodiments, the oligonucleotide may be found in the sequence which encodes Sequence ID Nos. 2, 4, 6, 8, 10, 12, 14, or 16. Within certain embodiments, the oligonucleotide is at least 15, 20, 30, 50, or 100 nucleotides in length. Within further embodiments, the oligonucleotide is labeled with another molecule (e.g., an enzyme, fluorescent molecule, or radioisotope). Also provided are primers which are capable of specifically amplifying all or a portion of the above-mentioned nucleic acid molecules which encode TGF-beta binding-proteins. As utilized herein, the term xe2x80x9cspecifically amplifyingxe2x80x9d should be understood to refer to primers which amplify the S aforementioned TGF-beta binding-proteins, and not other TGF-beta binding proteins such as Dan, Cerberus, Gremlin, or SCGF (U.S. Pat. No. 5,780,263).
Within related aspects of the present invention, methods are provided for detecting a nucleic acid molecule which encodes a TGF-beta binding protein, comprising the steps of incubating an oligonucleotide as described above under conditions of high stringency, and detecting hybridization of said oligonucleotide. Within certain embodiments, the oligonucleotide may be labeled and/or bound to a solid support.
Within other aspects of the present invention, ribozymes are provided which are capable of cleaving RNA which encodes one of the above-mentioned TGF-beta binding-proteins (e.g., Sequence ID NOs. 2, 6, 8, 10, 12, 14, or 16). Such ribozymes may be composed of DNA, RNA (including 2xe2x80x2-O-methyl ribonucleic acids), nucleic acid analogs (e.g., nucleic acids having phosphorothioate linkages) or mixtures thereof. Also provided are nucleic acid molecules (e.g., DNA or cDNA) which encode these ribozymes, and vectors which are capable of expressing or producing the ribozymes. Representative examples of vectors include plasmids, retrotransposons, cosmids, and viral-based vectors (e.g., viral vectors generated at least in part from a retrovirus, adenovirus, or, adeno-associated virus). Also provided are host cells (e.g., human, dog, rat, or mouse cells) which contain these vectors. In certain embodiments, the host cell may be stably transformed with the vector.
Within further aspects of the invention, methods are provided for producing ribozymes either synthetically, or by in vitro or in vivo transcription. Within further embodiments, the ribozymes so produced may be further purified and/or formulated into pharmaceutical compositions (e.g, the ribozyme or nucleic acid molecule encoding the ribozyme along with a pharmaceutically acceptable carrier or diluent). Similarly, the antisense oligonucleotides and antibodies or other selected molecules described herein may be formulated into pharmaceutical compositions.
Within other aspects of the present invention, antisense oligonucleotides are provided comprising a nucleic acid molecule which hybridizes to a nucleic acid molecule according to Sequence ID NOs. 1, 3, 5, 7, 9, 11, 13, or 15, or the complement thereto, and wherein said oligonucleotide inhibits the expression of TGF-beta binding protein as described herein (e.g., human BEER). Within various embodiments, the oligonucleotide is 15, 20, 25, 30, 35, 40, or 50 nucleotides in length. Preferably, the oligonucleotide is less than 100, 75, or 60 nucleotides in length. As should be readily evident, the oligonucleotide may be comprised of one or more nucleic acid analogs, ribonucleic acids, or deoxyribonucleic acids. Further, the oligonucleotide may be modified by one or more linkages, including for example, covalent linkage such as a phosphorothioate linkage, a phosphotriester linkage, a methyl phosphonate linkage, a methylene(methylimino) linkage, a morpholino linkage, an amide linkage, a polyamide linkage, a short chain alkyl intersugar linkage, a cycloalkyl intersugar linkage, a short chain heteroatomic intersugar linkage and a heterocyclic intersugar linkage. One representative example of a chimeric oligonucleotide is provied in U.S. Pat. No. 5,989,912.
Within yet another aspect of the present invention, methods are provided for increasing bone mineralization, comprising introducing into a warm-blooded animal an effective amount of the ribozyme as described above. Within related aspects, such methods comprise the step of introducing into a patient an effective amount of the nucleic acid molecule or vector as described herein which is capable of producing the desired ribozyme, under conditions favoring transcription of the nucleic acid molecule to produce the ribozyme.
Within other aspects of the invention transgenic, non-human animals are provided. Within one embodiment a transgenic animal is provided whose germ cells and somatic cells contain a nucleic acid molecule encoding a TGF-beta binding-protein as described above which is operably linked to a promoter effective for the expression of the gene, the gene being introduced into the animal, or an ancestor of the animal, at an embryonic stage, with the proviso that said animal is not a human. Within other embodiments, transgenic knockout animals are provided, comprising an animal whose germ cells and somatic cells comprise a disruption of at least one allele of an endogenous nucleic acid molecule which hybridizes to a nucleic acid molecule which encodes a TGF-binding protein as described herein, wherein the disruption prevents transcription of messenger RNA from said allele as compared to an animal without the disruption, with the proviso that the animal is not a human. Within various embodiments, the disruption is a nucleic acid deletion, substitution, or, insertion. Within other embodiments the transgenic animal is a mouse, rat, sheep, pig, or dog.
Within further aspects of the invention, kits are provided for the detection of TGF-beta binding-protein gene expression, comprising a container that comprises a nucleic acid molecule, wherein the nucleic acid molecule is selected from the group consisting of (a) a nucleic acid molecule comprising the nucleotide sequence of SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, or 15; (b) a nucleic acid molecule comprising the complement of the nucleotide sequence of (a); (c) a nucleic acid molecule that is a fragment of (a) or (b) of at least 15, 20 30, 50, 75, or, 100 nucleotides in length. Also provided are kits for the detection of a TGF-beta binding-protein which comprise a container that comprise one of the TGF-beta binding protein antibodies described herein.
For example, within one aspect of the present invention methods are provided for determining whether a selected molecule is capable of increasing bone mineral content, comprising the steps of (a) mixing one or more candidate molecules with TGF-beta-binding-protein encoded by the nucleic acid molecule according to claim 1 and a selected member of the TGF-beta family of proteins (e.g., BMP 5 or 6), (b) determining whether the candidate molecule alters the signaling of the TGF-beta family member, or alters the binding of the TGF-beta binding-protein to the TGF-beta family member. Within certain embodiments, the molecule alters the ability of TGF-beta to function as a positive regulator of mesenchymal cell differentiation. Within this aspect of the present invention, the candidate molecule(s) may alter signaling or binding by, for example, either decreasing (e.g., inhibiting), or increasing (e.g., enhancing) signaling or binding.
Within yet another aspect, methods are provided for determining whether a selected molecule is capable of increasing bone mineral content, comprising the step of determining whether a selected molecule inhibits the binding of TGF-beta binding-protein to bone, or an analogue thereof. Representative examples of bone or analogues thereof include hydroxyapatite and primary human bone samples obtained via biopsy.
Within certain embodiments of the above-recited methods, the selected molecule is contained within a mixture of molecules and the methods may further comprise the step of isolating one or more molecules which are functional within the assay. Within yet other embodiments, TGF-beta family of proteins is bound to a solid support and the binding of TGF-beta binding-protein is measured or TGF-beta binding-protein are bound to a solid support and the binding of TGF-beta proteins are measured.
Utilizing methods such as those described above, a wide variety of molecules may be assayed for their ability to increase bone mineral content by inhibiting the binding of the TGF-beta binding-protein to the TGF-beta family of proteins. Representative examples of such molecules include proteins or peptides, organic molecules, and nucleic acid molecules.
Within other related aspects of the invention, methods are provided for increasing bone mineral content in a warm-blooded animal, comprising the step of administering to a warm-blooded animal a therapeutically effective amount of a molecule identified from the assays recited herein. Within another aspect, methods are provided for increasing bone mineral content in a warm-blooded animal, comprising the step of administering to a warm-blooded animal a therapeutically effective amount of a molecule which inhibits the binding of the TGF-beta binding-protein to the TGF-beta super-family of proteins, including bone morphogenic proteins (BMPs). Representative examples of suitable molecules include antisense molecules, ribozymes, ribozyme genes, and antibodies (e.g., a humanized antibody) which specifically recognize and alter the activity of the TGF-beta binding-protein.
Within another aspect of the present invention, methods are provided for increasing bone mineral content in a warm-blooded animal, comprising the steps of (a) introducing into cells which home to the bone a vector which directs the expression of a molecule which inhibits the binding of the TGF-beta binding-protein to the TGF-beta family of proteins and bone morphogenic proteins (BMPs), and (b) administering the vector-containing cells to a warm-blooded animal. As utilized herein, it should be understood that cells xe2x80x9chome to bonexe2x80x9d if they localize within the bone matrix after peripheral administration. Within one embodiment, such methods further comprise, prior to the step of introducing, isolating cells from the marrow of bone which home to the bone. Within a further embodiment, the cells which home to bone are selected from the group consisting of CD34+ cells and osteoblasts.
Within other aspects of the present invention, molecules are provided (preferably isolated) which inhibit the binding of the TGF-beta binding-protein to the TGF-beta super-family of proteins.
Within further embodiments, the molecules may be provided as a composition, and can further comprise an inhibitor of bone resorption. Representative examples of such inhibitors include calcitonin, estrogen, a bisphosphonate, a growth factor having anti-resorptive activity and tamoxifen.
Representative examples of molecules which may be utilized in the afore-mentioned therapeutic contexts include, e.g., ribozymes, ribozyme genes, antisense molecules, and/or antibodies (e.g., humanized antibodies). Such molecules may depending upon their selection, used to alter, antagonize, or agonize the signalling or binding of a TGF-beta binding-protein family member as described herein
Within various embodiments of the invention, the above-described molecules and methods of treatment or prevention may be utilized on conditions such as osteoporosis, osteomalasia, periodontal disease, scurvy, Cushing""s Disease, bone fracture and conditions due to limb immobilization and steroid usage.
These and other aspects of the present invention will become evident upon reference to the following detailed description and attached drawings. In addition, various references are set forth herein which describe in more detail certain procedures or compositions (e.g., plasmids, etc.), and are therefore incorporated by reference in their entirety.